I have a '96 Rexhall with the 454 eng. The transmission went to 350 degrees on flat highway towing nothing in cruise control. This happened on 1 short trip and then the next trip I'll describe- I shifted down to D not OD, and it stayed there. Then when I hit the mountains, I pushed it hard and the temp went down to 160 degrees and stayed there until I parked. On the trip home, It never went over 160 degrees. Downhill, uphil, onthe freeway in D and OD - it never changed. Do you suppose that a filter was plugged in the transmission and the hill torture test cleared it out?